A base station can perform, by using a cellular link, data communication with user equipment (UE) located in a cell of the base station. As shown in FIG. 1, UE 30 is located in a cell 40 of a base station 10, and then uplink and downlink data is transmitted between the base station 10 and the UE 30 by using a cellular link.
However, because UE 20 is located in a cell 60 of a base station 50, data communication cannot be directly performed between the base station 10 and the UE 20. Instead, the data transmission between the base station 10 and the UE 20 needs to be performed via the base station 50. For example, if the UE 20 needs to send uplink data to the base station 10, the UE 20 first needs to send the uplink data to the base station 50 by using a cellular link, and then the base station 50 forwards the uplink data to the base station 10. For example, if the base station 10 needs to send downlink data to the UE 20, the base station 10 first needs to send the downlink data to the base station 50, and then the base station 50 forwards the downlink data to the UE 20 by using a cellular link.
In this way, not only cellular link congestion is caused, but also a delay of data transmission is long. Consequently, data transmission efficiency is low.